In general, data in digital format has a low noise level when being transmitted, stored and processed, and thus is used in various fields of electronics which require stable signal processing. However, the data in digital format needs to be converted into data in analog format when the digital data is applied to analog devices such as radars and displays. Here, a digital-to-analog converter (DAC) may be employed for converting a digital electrical signal into an analog electrical signal. The DAC should have a data conversion rate that is high enough to enable high-speed data transmission, storage and processing. Recently, research on high-speed DACs, including attempts to apply photonics technology to DACs, is being actively conducted.
A photonic DAC (PDAC) has high-speed sampling, a wide bandwidth and reduced interference, and thus is an attractive candidate for next-generation DACs. An example of a PDAC technology is described in the Institute of Electrical and Electronics Engineers (IEEE) Photonics Technology Letters, v. 15, n. 1, p. 117, January 2003, by Araz Yacoubian, et al., which describes a PDAC technique employing a weighted 1×N coupler and a multiple number of electro-optic polymer modulators. Mach-Zehnder modulators (MZMs) are used as the electro-optic polymer modulators. The weighted 1×N coupler divides a continuous wave (CW) laser beam into N beams having various intensities. Another example of a PDAC technology is described in Electronics Letters, v. 43, n. 19, p. 1044, September 2007, by X. Yu, et al., which describes a PDAC technique employing a weighted 1×N coupler and a multiple number of MZMs.